2 Mechatronics

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Prepared byOnipede Bamidele O. and Omole, Femi O. 1Prototype Engineering Development Infrastructure (PEDI), Ilesa, Osun State

National Agency for Science and Engineering Infrastructure (NASENI)

MECHATRONICS: AN OVERVIEW

Mechatronics, the term coined in Japan in the 1970s, has evolved over the past

25 years and has led to a special breed of intelligent products.

Mechatronics is a natural stage in the evolutionary process of modern

engineering design. It is the synergetic integration of mechanical engineering

with electronics and intelligent computer control in the design and

manufacturing of industrial products and processes.

Mechatronics is an interdisciplinary field, in which the following disciplines act

together (see Figure (A) below):

Mechanical Systems (Mechanical Elements, Machines, and Precision

Mechanics);

Electronic Systems (Microelectronics, Power Electronics, Sensor and Actuator

Technology); and

Information Technology(Systems Theory, Automation, Software Engineering,

Artificial Intelligence).


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Figure (A): Mechatronics: Synergetic integration of different disciplines

WHY MECHATRONICS?

We have to ask ourselves, why is it so important for the Industry to keep the

know-how of their employees and staff permanently up-to-date. Why should

the Industry send participants for a short-term training program to a Centre of

Excellence, with Trainers who are certified according to international and

professional standard? The reasons are not far-fetched.

I. Continuous learning. This is essential because:i. Product Lifecycle

Innovations and trends reduce the lifecycle of a product dramatically.

Production systems have to be flexible to be able to react as fast as possible.


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ii. ProductivityNew trends and technological developments can increase the productivity and

your standing in the global market.

II. Automation technology. This is required because ofi. Globalization

The global market requests for availability, quality, reasonable prices and

services.

ii. ProductivityIncrease the Productivity by producing on a higher level of Automation. The

key factors of Productivity are:

Quality Time Costs

Mechatronics Training is important to be able to handle automated and

networked systems. To do so a new way of thinking and acting is required

Mechatronics.

The technological parts which have to be handled are Factory and Process

Automation.


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TYPES OF AUTOMATION

There are two parts of automation processes in industry.

Factory Automation

This is the handling of solid workpieces through-out the entire manufacturing

process, by means of which, in each step of the process, the shape, dimension,

orientation and material is known.

Process Automation

This is the handling of all flowing materials, fluids or powdery, in manual or

automated processes i.e. the production, transportation, treatment and

disposal. Mostly closed loop controllers are used within the Process

Technology to control pressure, level, flow, temperature etc.

Figure (B) shows both Factory and Process Automation Setup.


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Figure (B): Factory and Process Automation Setup

MECHATRONICS STRUCTURE

The training conception of Mechatronics is divided into three levels with the

focus on technology and competence.


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BASIC TECHNOLOGIES

The basic training technologies are:

Mechanics Electrics/Electronics Pneumatics Hydraulics Sensorics Controllers Robotics CAD/CAM/CNC IT

Partly Automation

This represents the production process steps of:

Storage/Retrieval Quality Transportation Processing Handling


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Assembly

Fully Automation

This represents the interaction of the single production steps to an entire

production process. The focus here is on:

Installation and Commissioning Programming and Communication Maintenance and Trouble Shooting

Figure (C): Full Automation Setup

PLANNING AND DESIGN

This is the process involved in the arrangement of the laboratory. The

following points should be noted as a rule:


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The laboratory should be symmetrical. No cables should lie around the floor naked. Good colour separation The laboratory should be beautiful and neat

INSTALLATION AND COMMISIONING

Installation involves the coupling of all station, components and parts. The

bringing together of all the separate units of any production line is called

Assembly.

Commissioning is the process of ensuring that all component parts are in good

working condition i.e. sensors, switches, and connections.

There are three types of commissioning:

Pneumatic commissioning: to ensure good regulation of air pressure,absence of all leaks.

Mechanical commissioning: to ensure the right alignment of allmechanical parts.


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Electrical commissioning: to ensure good electrical connections of thewires and cables to the appropriate terminals. The driving voltage of the

setup is 24 Volts.

PROGRAMMING AND COMMUNICATION

DIGITAL TECHNOLOGY: LOGIC GATES

Logic gates are the basic building blocks of logic circuits and a computer.

Mechatronic systems have a central computational element as well as specific

logic functions implemented in hardware. A logic circuit consists of several

logic gates working together. Logic operations can be subdivided into two

categories, namely, combinational and sequential. In combinational logic

circuits, the logic gates are used to produce an output based on instantaneous

values of the inputs, whereas in the sequential logic circuits, the change in

output depends on the present state as well as the state before the changes in

input values, thus exhibiting memory behavior. Furthermore, the sequential

logic circuits can be synchronous or asynchronous. When the output changes

synchronously with a clock input, it is said to be synchronous. When the inputs

are read as soon as there is any change in it, it is called an asynchronous logic

circuit.


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There are three fundamental logic operations, namely AND, OR, and NOT

functions. Other logic operations are derived from these fundamental ones.

The AND gate symbol and its truth table are shown in Figure (D).

Input A Input B Output Q

0 0 0

0 1 0

1 0 0

1 1 1

Figure (D): Truth table and symbol for two input AND logic gate

The AND gate can have more than two inputs.

Figure (E) shows an OR gate. Here the output is 1 when either of the inputs or

both inputs are 1.

Figure (E): Truth table and symbol for two input OR logic gate

Input A Input B Output Q

0 0 0

0 1 1

1 0 1

1 1 1


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The OR gate can also have more than two inputs.

Figure (F) shows an inverter, also known as a NOT gate. This gate takes one

input and simply inverts the logic, that is, a 1 input is returned as 0 output and

vice versa.

Figure (F): Truth table and symbol for NOT logic gate

Other common logic gates that are derived from these fundamental ones are

NAND, NOR, and Exclusive OR gates. NAND gate is a combination of AND and

NOT gates; NOR is a combination of OR and NOT gates, and Exclusive OR can

be generated with a combination of OR, NAND, and AND gates.

The logic functions and their implementation into hardware using gates is the

basic building block of a digital computer.

PROGRAMMING LANGUAGES

Programming languages for PLCs are described in IEC-1131-3 nomenclature:

LDLadder Diagram

Input Output

1 0

0 1


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ILInstruction List (An Assembler) SFCSequential Functions Chart STStructured Text (similar to a high level language) FBDFunction Block Diagram

BIT, BYTE WORD PROCESSING IN MECHATRONICS

BIT: The simplest form of data is one bit, which can take one of the two values

0 or 1, and hence is called binary data. All information in modern digital

computers is stored in binary form.

BYTE: A fixed number of bits (usually 8), which can be treated by a computer as

a unit.

One byte = 8bits

One word = 2 bytes = 16 bits

Q (B, W) - Output (Byte, Word)

In the PLC, the first byte is for the station while the second is for the control

panel.

PROGRAMS IN A CPU

A CPU will principally run two different programs:

The operating system and


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User Program

The user program can be created and downloaded to the CPU. It contains all

the functions required to process specific automation task. The tasks of the

user program include:

Processing process data (for example, generating logical links of binary

signals, fetching and evaluating analog signals, specifying binary signals for

output, output of analog values)

Reaction to interrupts

Handling disturbances in the normal program cycle.

Blocks in the User Program

The STEP 7 programming software allows the structuring of the user program,

in other words to break down the program into individual, self-contained

program sections. This has the following advantages:

Extensive programs are easier to understand.

Individual program sections can be standardized.

Program organization is simplified.

It is easier to make modifications to the program.

Debugging is simplified since separate sections can be tested.

Commissioning of the system is made much easier.


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The program sections of a structured user program correspond to these

individual tasks and are known as the Blocks of a program.

Block Types

There are several different types of blocks you can use within an S7 user

program:

Block Brief Description of Function

Organization Blocks (OB) OBs determine the structure of the user program.

System Function Blocks

(SFB) and System Functions

(SFC)

SFBs and SFCs are integrated in the S7 CPU and allow the

access to some important system functions.

Function Blocks (FB) FBs are blocks with a "memory" which can be programmed

by the user.

Functions (FC) FCs contain program routines for frequently used functions.

Instance Data Blocks

(Instance DB)

Instance DBs are associated with the block when an FB/SFB

is called. They are created automatically during compilation.

Data Blocks (DB) DBs are data areas for storing user data. In addition to the

data that are assigned to a function block, shared data can

also be defined and used by any blocks.


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OBs, FBs, SFBs, FCs, and SFCs contain sections of the program and are

therefore also known as Logic Blocks. The permitted number of blocks per

block type and the permitted length of the blocks is CPU-specific.

Organization Blocks (OBs) represent the interface between the operating

system and the user program. They are called by the operating system; and

control cyclic and interrupt-driven program execution, startup behavior of the

PLC and error handling. Organization Blocks can be programmed to determine

CPU behaviour.

STRUCTURAL PROGRAMMING

The entire user program can be written in OB1 (linear programming). This is

only advisable with simple programs written for the S7-300 CPU and requiring

little memory. Complex automation tasks can be controlled more easily by

dividing them into smaller tasks reflecting the technological functions of the

process. These tasks are represented by corresponding program sections,

known as the Blocks (Structured Programming).

Let the programming begin!

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